The midgut ultrastucture of the third-instar of Dermatobia hominis (L., Jr.) was investigated using transmission electron microscopy (TEM). The tubular midgut bears a monolayer of epithelial cells with the plasma membrane showing multiple folding where it adjoins the basement membrane. Septate junctions bound the epithelial cells on each side. These cells have electrolucent cytoplasm containing mitochondria, vacuoles, rough and smooth endoplasmic reticula, lamellar bodies, and a prominent nucleus with dispersed chromatin. The peritrophic matrix is close to elongate microvilli, which are sometimes forked. Regenerative cells, in an undifferentiated state when closest to the basement membrane, are scattered throughout the epithelial cells. A thick basement membrane, surrounded by thick connective tissue including muscle, tracheal tubes, and extracellular matrix is linked to epithelial cells by hemidesmosome-like structures. Entero-endocrine, goblet or cuprophilic cells were not observed.